1. Field of the Invention
The present invention relates to an apparatus and a method of manufacturing a liquid crystal display by bonding two transparent substrates in a vacuum, and particularly, to an apparatus and a method of manufacturing a liquid crystal display, which makes it possible to easily perform an alignment with high precision in a short time.
2. Description of the Related Art
Conventionally, as a method of manufacturing a liquid crystal display, there has been a method having the steps of forming a sealing material between two substrates and injecting a liquid crystal into the inside thereof as described below. Hereinafter, this manufacturing method is referred to as xe2x80x9ca first prior artxe2x80x9d. FIG. 1 is a flowchart showing the method of manufacturing a liquid crystal display according to the first prior art.
First, two substrates are provided. On one surface of one substrate, a thin film transistor (TFT) is formed in an array shape. Hereinafter, this substrate is referred to as xe2x80x9ca TFT substratexe2x80x9d. On one surface of the other substrate, a color filter (CF) is formed. Hereinafter, this substrate is referred to as xe2x80x9ca CF substratexe2x80x9d. Thereafter, an orientation film is formed on both the TFT substrate and the CF substrate (step S1). Next, spacers are formed on the surface of the CF substrate on which the CF is formed (step S2a), and a sealing material having an injection hole in part is formed in a rectangular shape on the surface of the first substrate (the TFT substrate) on which the TFT is formed (step S2b). Thereafter, the surfaces of the second substrate (the CF substrate) and the first substrate on which the CF and the TFT are respectively formed are opposed to each other, and then superposed one on another (step S3). Subsequently, these are heated so that the sealing material formed in the first substrate is burned (step S4).
Thereafter, the superposed first and second substrates are cut and divided into the predetermined number of panels (step S5). Then, a liquid crystal is injected into the inside through the injection hole provided in the sealing material (step S6). Thereafter, the injection hole is sealed (step S7). And then, a cleaning of the panel is performed in order to eliminate contamination made by the liquid crystal injection and the like (step S8). Thereafter, a polarizing plate is attached thereon, and a driving circuit and the like are installed, thereby a liquid crystal display is completed.
However, in the first prior art, there is a problem that there are too many steps.
Therefore, recently, in the standpoint of reducing the number of steps, a manufacturing method having the steps of dropping a liquid crystal in a TFT substrate and bonding the TFT substrate and a CF substrate in a vacuum has been developed and known. Hereinafter, this manufacturing method is referred to as xe2x80x9ca second prior artxe2x80x9d. FIG. 2 is a flowchart showing the method of manufacturing a liquid crystal display according to the second prior art.
First, as in the first prior art, two substrates are provided. After that, an orientation film is formed on both a first substrate (a TFT substrate) and a second substrate (a CF substrate) (step S11). Next, spacers are formed on the surface of the second substrate on which the CF is formed (step S12a), and a sealing material composed of a photo-curable resin is formed in a rectangular shape on the surface of the first substrate on which the TFT is formed (step S12b). Thereafter, a liquid crystal is dropped inside of the sealing material in the first substrate, and the surfaces of the second substrate and the first substrate on which the CF and the TFT are respectively formed are opposed in a vacuum and aligned, and pressed each other, and then the vacuum is ventilated (released to the atmosphere), so that the second substrate and the first substrate are fixed by an atmospheric press (step S13).
Next, the sealing material is irradiated by ultraviolet rays to become a semi-cured state (step S14). Subsequently, the sealing material is heated to be thermally cured (step S15). Then, the bonded first and second substrates are cut and divided into the predetermined number of panels (step S16). Thereafter, a polarizing plate is attached thereon, and a driving circuit and the like are installed, thereby a liquid crystal display is completed.
FIG. 3 is a cross sectional view showing the structure of an apparatus for manufacturing a liquid crystal display used in the second prior art.
In the conventional apparatus for manufacturing a liquid crystal display, there is provided with a vacuum chamber 111, and a first surface plate 112 and a second surface plate 113 are provided within the vacuum chamber 111 in parallel to each other. In the vacuum chamber 111, there are provided with a vacuum suction opening 111a and a vacuum exhaust opening 111b. The material for the first surface plate 112 is, for example, ceramics, and an electrode (the first substrate sucker) 114 for electrostatic suction of a first substrate 131 is padded in the surface opposite to the second surface plate 113. Likewise, the material for the second surface plate 113 is, for example, ceramics, and an electrode (the second substrate sucker) 115 for electrostatic suction of a second substrate 132 is padded in the surface opposite to the first surface plate 112. Also, in each of the first surface plate 112 and the second surface plate 113, inhalation holes (not shown) and the like for vacuum suction of the first substrate 131 and the second substrate 132 are provided.
Furthermore, the lower surface of the first surface plate 112 is connected to the upper end of a first surface plate-connecting pedestal 125, and the lower end of the first surface plate-connecting pedestal 125 is connected to a position-adjusting table 126. On the position-adjusting table 126, there is provided with a motor (not shown), which enables the first surface plate-connecting pedestal 125 to move straight in two directions perpendicular to each other (X direction and Y direction) and to rotate in a circumferential direction (xcex8 direction) having the central axis as a rotating axis. Therefore, the position of the first surface plate 112 and the first substrate 131 is adjusted by the position-adjusting table 126.
Further, there is provided with a pressing motor 127, which moves the second surface plate 113 in a vertical direction to press the second surface plate 113 and the first surface plate 112 each other. The pressing motor 127 is fixed to a fixing member 128a. Also, outside of the vacuum chamber 111, there are provided with an alignment camera 130 for detecting positions of alignment marks 133 and 134 respectively provided in the first substrate 131 and the second substrate 132, and an ultraviolet rays source 135 irradiating ultraviolet rays to a photo-curable resin 143 for tacking applied between the substrates Also, a second surface plate-supporting member 129, which supports the second surface plate 113 against the first surface plate 112 in parallel, is supported to a fixing member 128b. 
In addition, in the second prior art, although the CF substrate and the TFT substrate are pressed with superposed state in a vacuum, an alignment between the second substrate 132 (the CF substrate) and the first substrate 131 (the TFT substrate) is performed before being pressed. At this time, the gap between the second substrate and the first substrate is from about 0.2 to 0.5 mm. Further, the gap between the CF substrate and the TFT substrate, after being pressed by atmosphere (referred to as xe2x80x9can atmospheric pressxe2x80x9d), is about 5 xcexcm.
According to the second prior art, in comparison to the first prior art, there are advantages that the number of steps can be reduced, and because there is no process step of injecting a liquid crystal followed by superposing the substrates, the contamination therefrom can be prevented, and the material for sealing a hole thereafter is not needed.
Also, Japanese Patent Laid-Open No. 2000-66163 publication discloses a substrate-bonding apparatus, which bonds two substrates in a vacuum chamber by pressing the surface plates while checking the position of a mark using a recognition camera with the state of sucking the substrates to the surface plates by an electrostatic chuck.
However, in the second prior art, since the alignment is performed between the alignment marks provided in each of the substrate before pressing the surface plates, there is a problem that misalignment occurred by later pressurization needs to be corrected.
Also, in the substrate-bonding apparatus described in Japanese Patent Laid-Open No. 2000-66163 Publication, although the alignment is performed by fixing the substrates to the surface plates by the electrostatic suction, if the alignment is performed during the press, thrust is exerted in the direction parallel to a surface of the substrate, and if this thrust exceeds friction force having electrostatic suction and pressurizing force as drag, the position of the substrates is displaced. Therefore, it becomes necessary to precisely correct the misalignment plural times, and the number of steps increases. Further, in the worst case, there is a problem that the correction itself cannot be performed.
The object of this invention is to provide an apparatus and a method of manufacturing a liquid crystal display, which makes it possible to easily perform an alignment of two substrates with high alignment precision in a short time.
According to one aspect of the present invention, an apparatus for manufacturing a liquid crystal display constituted by bonding a first substrate and a second substrate disposed opposite to each other with a liquid crystal intervened between them, the apparatus comprises first and second surface plates having first and second substrate suckers disposed in parallel to each other. Each of the first and second substrate sucker sucks the first and second substrates, respectively. The apparatus further comprises: a vacuum chamber in which the first and second surface plates are provided; a first supporter which supports the first substrate with the state of restraining the displacement in a surface direction of the first substrate on the first surface plate; a second supporter which supports the second substrate with the state of restraining the displacement in a surface direction of the second substrate on the second surface plate; a pressurizer for press-welding the first and second substrates by pressing the first and second surface plates; and a position-aligning mechanism which performs an alignment between the first and second substrates while the pressurizer presses the first and second surface plates.
In the present invention, there are provided with the suckers for sucking the substrates to the surface plates, and supporters for supporting the substrates with the state of restraining the displacement in a surface direction of substrates on the surface plates, and a position-aligning mechanism for performing an alignment between the substrates while being pressed by the surface plates.
Thereby, although great force is applied from the pressurizer during the alignment, it is prevented that the substrates are displaced from the surface plates during the alignment because the first and second substrates are restrained in the direction parallel to the surface by the first and second supporters.
Moreover, in the vacuum chamber, the alignment between the first substrate and the second substrate is performed by the position-aligning mechanism in the state that a predetermined pressure is applied between the first surface plate and the second surface plate. Thereby, the misalignment between the first substrate and the second substrate does not occur although the press by the pressurizer is released.
In addition, by releasing the vacuum, since both substrates are subject to the press by atmospheric pressure (atmospheric press) as the state that an alignment is performed, very high precision is maintained. As a result, it becomes possible to perform the alignment with much ease and with high precision in a short time.
In case where each of the first and second substrates is electrostatically sucked to the first and second surface plates by the substrate sucker, it becomes possible to suck the substrates firmly even under low pressure in the vacuum chamber.
The first supporter may comprise: a first fixing member fixed on a surface of the first surface plate on which the first substrate sucker is provided, and having a plane vertical to the surface; a second fixing member fixed on a surface of the first surface plate on which the first substrate sucker is provided, and having a plane vertical to the surface of the first surface plate and the plane of the first fixing member; and a first squeezing mechanism which squeezes each of two sides of the first substrate perpendicular to each other on each of the planes of the first and second fixing mechanism. The second supporter may comprise: a third fixing member fixed on a surface of the second surface plate on which the second substrate sucker is provided, and having a plane vertical to the surface; a fourth fixing member fixed on a surface of the second surface plate on which the second substrate sucker is provided, and having a plane vertical to the surface of the second surface plate and the plane of the third fixing mechanism; and a second squeezing mechanism which squeezes each of two sides of the second substrate perpendicular to each other on each of the planes of the third and fourth fixing mechanism. In this case, the first and second squeezing mechanism may tightly squeeze two sides of the substrate on two fixing members in one direction, respectively, however, it is preferred to tightly squeeze them in two directions vertical to each of the planes of the fixing members because it is possible to more tightly squeeze the substrates on the fixing means.
According to another aspect of the present invention, an apparatus for manufacturing a liquid crystal display constituted by bonding a first substrate and a second substrate disposed opposite to each other with a liquid crystal intervened between them, the apparatus comprises: a liquid crystal dropping unit which drops a liquid crystal on the first substrate; a resin applying unit which applies a photo-curable resin on the first substrate; first and second surface plates having first and second electrostatic suckers disposed in parallel to each other. Each of the first and second electrostatic suckers sucks the first and second substrates, respectively. The apparatus further comprises: a vacuum chamber in which the first and second surface plates are provided; a first supporter which supports the first substrate with the state of restraining the displacement in a surface direction of the first substrate on the first surface plate; a second supporter which supports the second substrate with the state of restraining the displacement in a surface direction of the second substrate on the second surface plate; a pressurizer for press-welding the first and second substrates by pressing the first and second surface plates; a position-adjusting table for performing an alignment between the first and second substrates by sliding the first surface plate in two axial directions parallel to the surface of the first surface plate and in a circumferential direction having an axis vertical to the surface of the first surface plate as a rotating axis, while the pressurizer presses the first and second surface plates; and an ultraviolet irradiator which irradiates ultraviolet rays to the photo-curable resin in the state that the first and second substrates are press-welded.
Also, in this apparatus for manufacturing a liquid crystal display, although great force is applied from the pressurizer, it is prevented that the substrates are displaced from the surface plates during the alignment. Therefore, although the press by the pressurizer is released later, the misalignment between the first substrate and the second substrate does not occur, and very high precision is maintained. As a result, it becomes possible to perform the alignment with much ease and with high precision in a short time.
According to further another aspect of the present invention, a method of manufacturing a liquid crystal display constituted by bonding first and second substrates, the method comprises the steps of: dropping a liquid crystal on the first substrate; performing an alignment between the first and second substrates while pressing the second substrate on a surface of the first substrate on which the liquid crystal is dropped with a predetermined pressure in a vacuum chamber where the internal pressure is below a predetermined value; and releasing the vacuum chamber into atmospheric pressure.
According to further another aspect of the present invention, a method of manufacturing a liquid crystal display constituted by bonding first and second substrates, the method comprises the steps of: dropping a liquid crystal on the first substrate; applying a photo-curable resin on the first substrate; performing an alignment between the first and second substrates by sliding the first substrate in two axial directions parallel to the surface and in a circumferential direction having an axis vertical to the surface as a rotating axis, in a vacuum chamber where the internal pressure is below a predetermined value, while pressing the second substrate on a surface of the first substrate on which the liquid crystal is dropped with a predetermined pressure; irradiating ultraviolet rays to the photo-curable resin in the state that the first and second substrates are press-welded; and releasing the vacuum chamber into atmospheric pressure.
According to the methods of the present invention, in a vacuum chamber where the internal pressure is below a predetermined value, because the alignment between the first substrate and the second substrate is performed by being pressed, it is prevented that the substrates are displaced from the surface plates during the alignment although great force is applied to the substrates from the pressurizer. Therefore, although the press by the pressurizer is released later, the misalignment between the first substrate and the second substrate does not occur. In addition, by releasing the vacuum, because both substrates are subject to the press by atmospheric pressure (atmospheric press) as the state that the alignment is performed, very high precision is maintained. As a result, it becomes possible to perform the alignment with much ease and with high precision in a short time.
According to the present invention, because the substrates are subject to the atmospheric press by opening the vacuum chamber as the state that the alignment is performed, very high precision can be maintained. As a result, inconsistencies of display and color can be reduced. Also, comparing to the conventional method to inject a liquid crystal between substrates from a liquid crystal injection hole formed in a sealing material, contamination during the injection of liquid crystal can be prevented, and further, the number of processes can be reduced.